• Szabo Bogdan (19/19) May 06 2017 Hi,
• Adam D. Ruppe (4/5) May 06 2017 I believe that function is not marked pure if it is a SysTime
• Szabo Bogdan (3/8) May 06 2017 oh yes, I get it... begin and end are `SysTime`.. there is any
• Adam D. Ruppe (8/10) May 06 2017 Don't use pure?
• Szabo Bogdan (2/12) May 06 2017 Thanks!
• Jonathan M Davis via Digitalmars-d-learn (10/20) May 06 2017 Not really, no.

Szabo Bogdan <szabobogdan3 gmail.com> writes:

Hi,

I'm trying to write a function that saves some structs as csv 
file:

```
string toCsv(const(StatStorage) storage) {
   return storage.values
     .map!(a => [ a.name, a.begin.toISOExtString, 
a.end.toISOExtString, a.status.to!string ])
     .map!(a => a.join(','))
     .join('\n');
}
```

I think that it's obvious that this function has no external 
state and from my understanding, it should be a pure function. 
But when I declare it as `pure` I get an error `Error: pure 
function 'trial.reporters.stats.toCsv' cannot call impure 
function 'std.array.join!(MapResult!(__lambda3, 
MapResult!(__lambda2, const(Stat)[])), char).join'`.

What am I missing here?

Adam D. Ruppe <destructionator gmail.com> writes:

On Saturday, 6 May 2017 at 13:19:17 UTC, Szabo Bogdan wrote:
 a.begin.toISOExtString,

I believe that function is not marked pure if it is a SysTime 
because it needs to pull global timezone info.

What is the type of a.begin?

Szabo Bogdan <szabobogdan3 gmail.com> writes:

On Saturday, 6 May 2017 at 13:21:10 UTC, Adam D. Ruppe wrote:
 On Saturday, 6 May 2017 at 13:19:17 UTC, Szabo Bogdan wrote:
 a.begin.toISOExtString,

 I believe that function is not marked pure if it is a SysTime 
 because it needs to pull global timezone info.

 What is the type of a.begin?

oh yes, I get it... begin and end are `SysTime`.. there is any 
workaround for this?

Adam D. Ruppe <destructionator gmail.com> writes:

On Saturday, 6 May 2017 at 14:14:41 UTC, Szabo Bogdan wrote:
 oh yes, I get it... begin and end are `SysTime`.. there is any 
 workaround for this?

Don't use pure?

I don't think any of the SysTime conversion methods are pure 
since all of them call C functions which pull from the time 
zone... even if you subclassed the timezone to be pure, SysTime 
wouldn't pick that up since it uses the impure interface.

I guess you could use a casted wrapper to hack in pure too, but 
I'd say just take the keyword off.

Szabo Bogdan <szabobogdan3 gmail.com> writes:

On Saturday, 6 May 2017 at 15:01:16 UTC, Adam D. Ruppe wrote:
 On Saturday, 6 May 2017 at 14:14:41 UTC, Szabo Bogdan wrote:
 oh yes, I get it... begin and end are `SysTime`.. there is any 
 workaround for this?

 Don't use pure?

 I don't think any of the SysTime conversion methods are pure 
 since all of them call C functions which pull from the time 
 zone... even if you subclassed the timezone to be pure, SysTime 
 wouldn't pick that up since it uses the impure interface.

 I guess you could use a casted wrapper to hack in pure too, but 
 I'd say just take the keyword off.

Thanks!

Jonathan M Davis via Digitalmars-d-learn writes:

On Saturday, May 6, 2017 2:14:41 PM CEST Szabo Bogdan via Digitalmars-d-
learn wrote:
 On Saturday, 6 May 2017 at 13:21:10 UTC, Adam D. Ruppe wrote:
 On Saturday, 6 May 2017 at 13:19:17 UTC, Szabo Bogdan wrote:
 a.begin.toISOExtString,

 I believe that function is not marked pure if it is a SysTime
 because it needs to pull global timezone info.

 What is the type of a.begin?

 oh yes, I get it... begin and end are `SysTime`.. there is any
 workaround for this?

Not really, no.

The SysTime operations should be pure so long as they don't involve the
TimeZone (e.g. adding and substracting is fine), but converting to a string
involves using the TimeZone, because it needs to convert the value from UTC
to whatever the time zone is. It would be nice if TimeZone operations could
be pure, but they fundamentally can't be because that doesn't work when
dealing with the system's local time.

- Jonathan M Davis